Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$39.82	13.403%	$45.1571	$45.16	$45.15	$45.20
Purchase #2	$9.30	7.134%	$9.9635	$9.96	$9.95	$10.00
Purchase #3	$233.39	3.803%	$242.2658	$242.27	$242.25	$242.30
Purchase #4	$145.58	13.699%	$165.523	$165.52	$165.50	$165.50
Purchase #5	$48.27	4.553%	$50.4677	$50.47	$50.45	$50.50
Purchase #6	$86.73	10.302%	$95.6649	$95.66	$95.65	$95.70
Purchase #7	$59.28	5.202%	$62.3637	$62.36	$62.35	$62.40
7 purchase totals =	$622.37		$671.4057	$671.40	$671.30	$671.60